Contents I. Introduction
In recent years, interests of transparent flexible plastic substrates with a transparent conducting oxide (TCO) layer such as tin-doped (ITO) have been increased in the fields of portable devices, roll-up displays, or conformable displays. Transparent conducting zinc oxide (ZnO) films have been studied extensively because they exhibit high optical transmission and electrical conduction and have great potential applications in photo-electronic devices such as solar cells and displays. In addition, ZnO films are more stable in activated hydrogen environments than other TCO films such as ITO and tin oxide . ZnO films also have a lower material cost and a lower deposition temperature when compared to ITO films [1]–[2] [3]. These advantages are of considerable interest for practical applications such as transparent electrodes, window material in displays, solar cells, and various opto-electronic devices [4]–[5] [6]. Transparent conducting films deposited on polymer substrates have many merits compared with those deposited on glass substrates; they are lightweight, of small volume, and can make the obtained devices foldable, and easy to carry. ITO films deposited on polymer substrates have been prepared by many techniques [7]–[8] [9]. Recently, aluminum-doped zinc oxide films (ZnO:Al or AZO) were also deposited on organic substrates [7]–[8] [9].
